Method for making yarn and products comprising same

ABSTRACT

The invention relates to a process for manufacturing a continuous yarn, and the product obtained from such process. A multiplicity of continuous filaments are formed by the mechanical drawing of a multiplicity of streams of molten thermoplastic(s) flowing from the orifices of at least one fiberizing device. A mixture, in the liquid state, is deposited on the surface of at least some of the filaments before they are brought together into at least one yarn. An absorbent mat may be continuously impregnated, with at least some of said mixture being continuously taken up by means of a rotating roller in contact with said mat, and using a sizing roller, said mixture may be deposited on the filaments while they are being drawn.

FIELD OF THE INVENTION

The present invention relates to the field of reinforcing fibers and ofcomposites and, in particular, to the deposition of size compositions onglass filaments (or yarns).

BACKGROUND OF THE INVENTION

The manufacture of reinforcing glass yarns is carried out, in a knownway, starting from streams of molten glass flowing out of the orificesof bushings. These streams are drawn in the form of continuousfilaments, and these filaments are then brought together into baseyarns, which are then collected.

Before they are brought together into the form of yarns, the filamentsare coated with a size by passing over a sizer. This deposition isnecessary for obtaining the yarns and allows them to be combined withother organic and/or inorganic materials in order to produce composites.

The size firstly acts as a lubricant and protects the yarns from theabrasion that results from high-speed friction between the yarns andvarious devices during the aforementioned process.

The size may also, especially after it has cured, provide theaforementioned yarns with integrity, i.e. the mutual bonding of thefilaments within the yarns. This integrity is especially desired intextile applications in which the yarns are subjected to high mechanicalstresses. This is because, if the filaments are poorly held together,they break more easily and disrupt the operation of the textilemachinery. What is more, nonintegrated yarns are considered to bedifficult to handle.

However, the size is also employed in cases in which this integrity isnot desired, such as in the case of reinforcing fibers, when a high rateof impregnation with the material to be reinforced is desired. Thus, inthe manufacture, for example, of pipes using direct impregnation andfilament winding techniques, open yarns in which the filaments areseparated from one another are used. Small quantities of size,especially less than 0.5% by weight, are then used.

The size also facilitates the wetting and/or impregnation of the yarnsby the materials to be reinforced and helps to create bonds between saidyarns and said materials. The mechanical properties of the compositesobtained from the material and from the yarns depend in particular onthe quality of the adhesion of the material to said yarns and on theability of said yarns to be wetted and/or impregnated by said material.

Most sizes currently used are aqueous sizes which are simple to handlebut which must be deposited in large quantities on the filaments inorder for them to be effective. Water generally represents more than 90%by weight of these sizes (especially for viscosity reasons), and thismeans that the yarns have to be dried before they are used, it beingpossible for water to impair the good adhesion between the yarns and thematerials to be reinforced. These drying operations are lengthy andexpensive and their effectiveness is not always optimal; they requirethe use of large-capacity ovens. In addition, when they are carried outduring the fiber-forming operation (that is to say before the yarnsobtained by converging the filaments have been collected), either onfilaments (WO 92/05122) or on yarns (U.S. Pat. No. 3,853,605), theyrequire the installation of dryers under each bushing and, when they arecarried out on yarn packages, they run the risk of causing irregularand/or selective migration of the components of the size within thepackages (aqueous sizes already have a tendency to be distributed overthe yarns in an irregular manner because of their nature) and possiblyof causing yarn-coloration or package-distortion phenomena. Moreover,without drying, package distortion is often observed on straight-sidedpackages (rovings) of fine yarns (i.e. yarns having a “count” or “lineardensity” of 300-600 tex (g/km) or less) which are coated with aqueoussizes.

It is to remedy these drawbacks that a novel type of size, which isvirtually free of solvents and called an anhydrous size, has beendeveloped. Anhydrous sizes are curable and/or crosslinkable solutionswhich optionally contain organic solvents and/or water in small amounts,generally of less than 5% by weight. They are distinguishedadvantageously from aqueous sizes by their ability to be distributed ina homogeneous and uniform manner on the surface of the filaments, i.e.forming films of constant thickness, and by the fact that they make anysubsequent drying or solvent-removal treatment unnecessary since thesmall quantities of solvent evaporate during deposition of the size onthe filaments and during curing of the size.

Furthermore, the quantities of anhydrous size deposited on the filamentsare 30′ much less than those of aqueous size; thus, when depositing bymeans of a sizing roller, a film is formed on the surface of the latterwith a thickness not exceeding 15 μm in the case of an anhydrous sizeinstead of a film with a thickness of approximately 90 μm in the case ofan aqueous size. Moreover, these small quantities of anhydrous size aredeposited on the filaments with a much higher efficiency, possiblyreaching 100% when the operating conditions are chosen judiciously,whereas this efficiency is generally about 40 to 75% with aqueous sizes.

Anhydrous sizes fall mainly into three categories.

The first category encompasses UV-curable sizes as described in patentEP 0 570 283 and comprising, for example:

-   -   at least one mono-unsaturated or polyunsaturated monomer and/or        oligomer of the polyester acrylate, epoxy acrylate, silicone        compound or urethane acrylate type;    -   at least one photoinitiator, such as benzoin, acetophenone,        benzophenone, sulphonylacetophenone and their derivatives, as        well as thioxanthones;    -   if necessary, at least one organic solvent; and, optionally,    -   additives such as at least a wetting agent, an adhesion        promoter, an antishrinkage agent, a compatibilizer consisting        especially of a silane.

The second family of anhydrous sizes is that of thermally curable and/orcrosslinkable sizes, as described in patent applications FR 2 713 625and 2 743 361.

By way of example, the basic system of these compositions comprises:

-   -   an acrylic component and a heat-activated radical-initiating        peroxide; or    -   an epoxy component and an anhydrous constituent which cure by        reacting with each other.

The third category of anhydrous sizes forms part of the teaching ofapplicant FR 97/05926: these are room-temperature curable sizes, thebasic systems of which may contain one or more homopolymerizablemonomers and/or at least two copolymerizable monomers which require noexternal supply of energy. In the case of copolymerization of twomonomers, these may be deposited on the filaments in the form of theirmixture in solution, immediately after this mixture has been formed, orin the form of a first stable solution containing a first monomermixture and of a second stable solution containing a second monomermixture. In the latter variant, the first solution is applied to thefilaments and the second is applied subsequently thereto, at the latestwhile the filaments are being combined into yarns. Be that as it may,the copolymerization generally starts on the filaments as soon as thefirst and second monomers come into contact with each other and, ifnecessary, with the required catalyst or catalysts.

The UV-radiation treatments and heat treatments required to cure thesizes of the two first types mentioned above are carried out in one stepor in several steps, after the filaments have been brought together intoyarns. Thus, depending on the envisaged use and on the nature of theyarns, an irradiation or heat pretreatment is sometimes carried out atthe time of collecting the yarns in various forms of packages, in orderto precure the size, the actual curing of which is carried out in asubsequent radiation or heat treatment when the yarn is unwound for thespecific application for which it is intended, namely a textileapplication or an application of reinforcing organic or inorganicmaterials. This is because the yarn coated with the as yet uncuredcomposition does not exhibit integrity in the ordinary sense of the termsince the sheathed filaments of which the yarn is composed may slip overeach other. This yarn can therefore be handled easily and, when it iswound in the form of packages, can be easily extracted from the packageswithout first having to undergo a treatment to cure the size. The yarncoated with the as yet uncured size composition has, moreover, a veryhigh capability of being wetted and impregnated by materials to bereinforced, it thus being possible for impregnation to take place morerapidly (increase in productivity) and the composites obtained thushaving a more homogeneous appearance and having certain of theirmechanical properties improved.

However, as described in patent EP-0 570 283, curing the size by the UVirradiation of a yarn in the form of a package may also have advantages.

With regard to depositing anhydrous sizes on glass filaments, severaltechniques are known. Thus, according to application FR 2 763 328already mentioned, this deposition is carried out with the aid of aroller or of a sprayer, with the aid of a device which also acts as aconverging means, or by the use of other yarns or filaments coated withthe composition and brought into contact with the glass filaments. Thelatter technique makes reference to the special case of producingcomposite yarns, consisting of comingled glass filaments andthermoplastic polymer filaments or yarns.

By definition, deposition by spraying is inevitably accompanied by quitea significant amount of loss of size; the recovery of this lostproportion, assuming that it is possible, constitutes a handicap.

The method of deposition by means of a roller or of a device forconverging the filaments into yarns consists of taking up size from asomewhat viscous and thick liquid film formed on a smooth surface,having ranges of physical properties, especially surface hardness andsurface microporosity, of the type of those of metal surfaces. Startingfrom the observation that the chemical nature of the anhydrous sizesallows them to be used in ever lower quantities, there is currently arequirement for a process for forming an ever thinner liquid film, ofperfectly uniform, controllable and reproducible thickness, on amacroscopically smooth surface of the metallic, ceramic or organic type.This is because it may be expected that the take-up of size onto thefilaments from such a film results in the filaments being coated with aminimum quantity of size, with an increased deposition efficiency, i.e.a reduction in the amount of size lost, and for this to be achievedunder completely controlled conditions. Finally, the aim is, of course,to obtain filaments and yarns, and reinforced materials containing them,which have sufficient, or at least preserved, mechanical properties oreven in certain respects novel mechanical properties.

Currently, there is no process making it possible to form, in acontrollable manner, a thin film of anhydrous size at the surface, forexample, of a metal roller. This is because the immersion of the lowerpart of the roller in the size solution coupled with the rotation of theroller results in the formation, at the surface of the roller, of alayer whose characteristics can be controlled only to a small extent byvarying the viscosity of the solution and the rate of rotation of theroller. The thickness of this layer is too great and irregular, and itis impossible to avoid loss of size, in the device for bringing thefilaments together into yarns or for collecting the yarns, by the sizebeing thrown off under the effect of the inherent centrifugal force atthe high winding rates employed.

Moreover, no system for depositing size on a sizing roller with the aidof a metering pump and of an injection nozzle has yet allowed theformation of the desired film.

Furthermore, the previously-mentioned patent EP 0 570 283 brieflymentions, in its part describing FIG. 1, a coating device 13 consistingof an applicator provided with a felt moistened with a reactive mixtureusing a metering pump. This is because the structure of a felt allows itto soak up a solution in a particularly homogeneous manner. However, thetake-up of size suggested by the European patent, from the felt onto theglass filaments, is not satisfactory in the context of the technicalproblem mentioned above since the deposition of the required smallquantities of size on the filaments could not be achieved except at thecost of the felt drying out somewhat, a situation which, given thenaturally irregular structure of the felt, the surface of which hasfibers of varied dimensions, directions or even textures, would run therisk of the glass filaments catching thereon and therefore the risk ofsaid filaments breaking. Only relatively large amounts of size can thusbe deposited in the manner described in the document.

According to an advantageous approach, application FR 2 767 539proposes, in a process for manufacturing a continuous yarn, whichconsists in forming a multiplicity of continuous filaments by themechanical drawing of a multiplicity of streams of moltenthermoplastic(s) (particularly molten glass), in depositing a mixture,in the liquid state, in particular an anhydrous size, on the surface ofthe filaments before they are brought together into at least one yarn,according to the following technique. A mat of mechanicallyheld-together fibers, of the felt or woven fabric type, is continuouslyimpregnated with the liquid mixture, at least some of which iscontinuously taken up by means of a rotating roller in contact with themat; it is by using this sizing roller that the mixture is deposited onthe filaments while they are being drawn. The material of the sizingroller is of course selected so as to withstand the abrasion due to therubbing of the filaments. This technique makes it possible to deposit onthe surface of the filaments quantities of size as low as 0.5 to 1% byweight with respect to the weight of the filaments, which quantities aresufficient in the case especially of currently known high-performanceanhydrous sizes, with a deposition efficiency close to or equal to 100%.A liquid film of anhydrous size with a constant thickness of less than 8μm may be formed on the surface of the sizing roller in a perfectlyreproducible and controllable manner. Since the loss of size is reducedpractically to nothing, a sizing rate as low as 160 to 350 g/h will besufficient for a bushing producing 800 kg of filaments per day.

Moreover, the French patent application discloses that the mat ispositioned in an inclined plane and is fed with size drop by dropflowing onto the upper part of the mat, so that the size diffuses overthe entire surface of the mat both under gravity and by a capillaryeffect. Furthermore, it should be pointed out that in the industrialimplementation of this technique the dimensions of the sizing roller andof the mat are necessarily greater than the surface area of all of thefilaments to be sized, as the latter are frequently subjected to lateraldisplacements, and it is necessary, of course, to ensure that all of thefilaments are at any moment in contact with the sizing roller, whichitself has to be provided with a uniform film of size over the entirepart of its surface in contact with the filaments. However, it is notpossible to prevent the lateral end regions of the sizing roller fromhardly or even never coming into contact with filaments, since theseregions are largely dimensioned in order to guarantee that the mixtureis deposited on all the filaments. One of the consequences of this isthe presence of a relatively stagnant mixture, both in these lateral endregions of the sizing roller and in the corresponding regions of themat. It has also been observed that in these regions the liquid mixturemay, depending on the type of size, undergo a reaction owing to theaction of external elements such as water, carbon dioxide and hightemperature, forming condensates or gels, this type of chemical reactionmoreover having a tendency to propagate toward the center of the mat andof the sizing roller, including in the regions of the latter whichactually participate in transferring the mixture onto the filaments.This phenomenon causes drying regions on the surface of the roller. Thisinsufficient presence of size results in imperfect protection of thefilaments, which is manifested by the formation of fuzz or the breakageof filaments in the sheet.

SUMMARY OF THE INVENTION

The present invention relates to a process for manufacturing acontinuous yarn, which consists in forming a multiplicity of continuousfilaments by the mechanical drawing of a multiplicity of streams ofmolten thermoplastic(s) flowing out of the orifices of at least onefiberizing device and which consists in depositing a mixture, in theliquid state, on the surface of at least some of the filaments beforethey are brought together into at least one yarn, and in which process:

-   -   an absorbent mat is continuously impregnated with the mixture in        the liquid state;    -   at least some of said mixture is continuously taken up by means        of a rotating roller in contact with said mat; and    -   using the sizing roller, said mixture is deposited on the        filaments while they are being drawn.

The invention resides particularly in the fact that the mat is driven inrotation about an axis parallel to that of the sizing roller.

This is because it has been found that such an arrangement naturallycauses the liquid mixture to flow from the lateral end regions of themat and of the sizing roller toward their central regions, preventingstagnation of the mixture and formation of gel which ensues in theselateral regions. Thus, a means is available which guarantees that thelateral regions of the sizing roller and of the mat are permanentlyprovided with fresh liquid mixture, in such a way that the residencetime of the size in the felt before being replenished is short enoughfor the various chemical reactions associated with the externalconditions to result in insignificant deterioration in the quality oftransfer of the size onto the roller. While solving the problem of gelformation, the process of the invention retains the qualities inherentin the pick-up of mixture by the roller of the type by contact with animpregnated mat, these abovementioned qualities being: homogeneity,fineness and uniformity of thickness of the skin of mixture on theroller and, finally, maximum efficiency and quality of deposition.

Preferably, the absorbent mat is:

-   -   either a mat of fibers held together mechanically, such as a        felt or a woven;    -   or one consisting of a compressible elastomeric spongy material,        especially a foam based on a polymer such as polyurethane,        poly(tetrafluoroethylene), polybutadiene, etc., possibly        reinforced, for example by a mesh of glass fibers.

In all cases, the mat must be inert to the sizing components, both fromthe chemical standpoint (destruction of polymeric chains, etc.) and themechanical standpoint (swelling, abrasion resistance, etc.).

When an elastomeric spongy material is employed, it preferably has ahigh enough density, with pore diameters of less than 200 micrometersdistributed relatively homogeneously, with a compressibility of 3 to 10times its volume. In particular, it is in the form of sleeves or bandsgenerally reinforced with a mesh of polymer (polyamide, polypropylene,polyethylene etc.) fibers, glass fibers, natural cellulose fibers, etc.,so as to eliminate the elongatability without impairing thecompressibility.

According to the most common method of implementation, all the filamentsconstituting the yarn are made of glass. However, the invention does notexclude the variant in which the yarn consists of glass filaments and oforganic filaments, only the glass filaments being provided with acoating of said mixture in the liquid state or, on the contrary, theorganic filaments also being provided with this coating, or with acoating of a different size, the various size compositions beingespecially capable of reacting with one another. Organic filamentsshould be understood to mean thermoplastic polymer filaments, such aspolypropylene, polyamide or polyester filaments. These polymer filamentsmay be sprayed between the already-sized glass filaments, before allthese filaments are brought together into a yarn, as described in patentEP 0 599 695.

Given the abovementioned properties of the anhydrous sizes, as well astheir excellent capability of wetting the filaments, it isunderstandable that the liquid mixture to be deposited on the filamentspreferably consists of such an anhydrous size, for the definition ofwhich reference is made to the contents of patent EP 0 570 283 and ofapplications FR 2 713 625, 2 743 361 and 2 763 328 which have alreadybeen mentioned.

According to other features o: the process of the invention, mentionedin increasing order of preference:

-   -   the surface of the mat and the surface of the sizing roller are        made to undergo translational movements of the same direction        along their line of contact;    -   in the same sense; and    -   in the latter case, the speed of translation of the surface of        the mat is from 0.5 to 50% of that of the translation of the        surface of the sizing roller. This arrangement is advantageous,        in particular should one or more filaments break; this is        because the filaments then have a tendency to adhere to the        sizing roller, but are pushed back into the line of contact of        the sizing roller with the mat because of the speed of        translation of the surface of the mat, which is less than that        of the roller. When on the contrary the speed of translation of        the surface of the mat is greater than that of the roller, any        broken filaments are likely to be entrained between the mat and        the roller, considerably complicating the procedures for        restoring continuous yarn manufacturing operations.

According to another embodiment, the surface of the mat and the surfaceof the sizing roller are made to undergo translational movements alongtheir line of contact in the same direction but in opposite senses. Thespeed of translation of the surface of the mat is then preferably lessthan 20% of that of the surface of the sizing roller. This is becausethe mixture in the liquid state firstly diffuses into the thickness ofthe mat and is then taken up by the sizing roller by capillary effect.It has been observed that, with too high a speed of the mat, thisprocess does not proceed sufficiently uniformly since the timeseparating the moment when the mixture in the liquid state comes intocontact with a point on the mat and the time when this point comes intocontact with the sizing roller becomes too short. As a result, theliquid film formed on the sizing roller is nonuniform.

Furthermore, a double or multiple application of the process of theinvention to the filaments while they are being drawn, before they arebrought together into yarn(s), for the purpose of transferring theretoliquid compositions capable of reacting with one another especially atambient temperature by the copolymerization of constituents belonging tosuch separate compositions, also forms part of the invention. In otherwords, the overall dimensions of the device necessary for implementingthe process of the invention in no way prevents two or more of thembeing combined in order to deposit a double coating or a multiplecoating on a single set of filaments, as described in application FR 2763 328.

In the case of such a double or multiple application, it is moreoverpossible, without departing from the scope of the invention, to applyone or more coatings of mixture by means of devices other than thatdescribed above, provided that the first of the coatings is applied bymeans of the mat and the sizing roller of the invention: this isbecause, to obtain a size coating of good quality on the filaments, thatis to say one which is homogeneous and of controllable and uniformthickness, it is the quality of the coating of the first sizingcomponent which is the most key, as is well known in the field inquestion. The excellence of the manner of deposition according to theinvention is such that it allows the use, for applying the second sizecoating and/or a subsequent coating, of devices which are relativelyunsophisticated but nevertheless capable of producing a size coating ofvery high final quality. This device may consist, for example, of agathering wheel and stationary return, equipped, in the bottom of itsgroove, with a channel for the inflow of mixture intended for the secondcoating or for a subsequent coating; it ensures that the filamentscoated beforehand with at least a first mixture do come into contactwith the subsequent mixture, simultaneously with the gathering of thefilaments into a yarn and possibly the return, that is to say the changein direction of the latter.

The yarns obtained by the process of the invention are generallycollected in the form of packages on rotating supports. The yarnsobtained according to the invention can be easily unwound from thepackages and can be easily handled.

The yarns may also be collected on receiving supports undergoingtranslational motion. They may in fact be thrown by a device, which alsoserves to draw them, onto the collecting surface which is movingtransversely to the direction of the sprayed filaments, for the purposeof obtaining a web of intermingled continuous yarns, called a “mat”. Theyarns may also be chopped before collecting by a device serving also todraw them.

The yarns obtained according to the invention may thus be in variousforms after collection, especially in the form of reels of continuousfilaments (rovings, cakes, cops, etc.), or in the form of chopped yarns,and may be brought together into the form of braids, tapes, mats ornetworks, these being in woven or nonwoven form, etc. The glassfilaments forming these yarns may have a diameter of between 5 and 30microns and the glass used for producing these filaments may especiallybe E glass, AR (alkali-resistant) C glass, R glass, Z glass, S glass, Dglass, etc.

The yarns obtained by the invention may be advantageously combined withvarious materials to be reinforced for the purpose of producingcomposite components which have good mechanical properties. Thecomposites are advantageously obtained by combining at least one of theglass yarns according to the invention with at least one organic and/orinorganic material, the glass content of these composites generallybeing between 20 and 80% by weight.

Consequently, the subject of the invention is also a product consisting,at least in part, of a yarn obtained by a process as described above.This yarn may or may not have been subjected to a subsequent chopping orweaving treatment, to mechanical spraying or to any other shapingprocess; optionally, it is mixed with an organic or inorganic materialin order to reinforce the latter.

This yarn has a low loss on ignition of at most 3% by weight and even,in many embodiments, at most equal to 1% by weight.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the invention will appear in light ofthe following description of the appended drawings in which:

FIG. 1 shows a diagrammatic representation of a first device forimplementing the process of the present invention;

FIG. 2 shows a diagrammatic representation of a second device forimplementing the process of the present invention; and

FIG. 3 shows a diagrammatic representation of a third device forimplementing the process of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The devices of the present invention comprise a tank 1 of sizeoptionally maintained at a constant temperature, ensuring that theproduct is well preserved, so as to guarantee that the meteringconditions remain stable.

According to FIG. 1, the size is drawn up by a pump 2 of the peristalticor diaphragm type, which subjects the fluids to particularly low shearstresses.

The quantity drawn up is transferred onto the distributing felt 10 afterhaving passed through a flow meter 3.

In addition, a microcomputer 4 is connected both to the flow meter 3 andto the pump 2 so as permanently to adapt the volume or the mass of sizedelivered by the pump 2 depending on the information supplied by theflow meter.

The devices shown in FIGS. 2 and 3 employ, for feeding the felt 10, acompressed-air supply 5 at the start of the fluid circuit upstream ofthe tank 1.

According to FIG. 2, the size coming from the tank 1 passes through aflow meter 3 and a regulating valve 6, both of these being connected toa microcomputer 4. This time, the microcomputer 4 uses the informationdelivered by the flow meter 3 to control, in real time, any correctionto the flow rate by means of the regulating valve 6.

This regulating function is provided, in the simplified device shown inFIG. 3, by a temperature-compensating volumetric regulating valve 7inserted in the fluid circuit between the pressurized-air supply 5 andthe tank 1. The valve 7, having an integrated and autonomous regulatingfunction, makes it unnecessary to use an auxiliary management andcontrol device of the computer type.

The felt 10 is a continuous band driven in rotation around two rollers14 and 15 of parallel axes. Another recommended variant consists inreplacing, for driving the continuous band, the two rollers 14 and 15 inthe figure with a single roller parallel to the latter and positioned soas to ensure that the felt 10 is in contact with the sizing roller 11.

The felt 10, uniformly fed with size, has the function of distributingthe latter over a portion of the surface of the sizing roller 11 whichis slightly larger than that with which the web of filaments 12,delivered by the bushing 13 and being drawn, is in contact. The sizingroller 11 has an axis parallel to those of the rollers 14 and 15 drivingthe felt 10.

The sizing roller 11 is driven in rotation in the directioncorresponding to the direction in which the filaments are drawn, and ata peripheral linear speed of 50 to 150 n/min (to be compared with therun speed of the filaments: 600 to 4000 m/min)

The position of the rollers 14 and 15 can be adjusted, thereby making itpossible to vary the inclination of the assembly which they form withthe felt 10, and the pressure exerted by this assembly on the sizingroller 11.

The felt 10 is driven in the direction corresponding to that of therotation of the sizing roller 11, and at a linear speed of 0.10 to 75m/min.

The flow of the size and its distribution in the felt 10 depend on theviscosity of the size, on the characteristics of the felt (nature of theconstituents, density, texture, dimensions), on the pressure that itexerts on the sizing roller and on the movement characteristics of thefelt and of the sizing roller.

The texture of the felt and the viscosity of the size are intimatelyconnected. For example, a dense felt will be wetted on the surface by aviscous size whereas a liquid size will easily penetrate a not verydense felt and will flow out of it without being distributed over itsentire width.

The inclination of the felt also plays an important role in distributingthe size by allowing the gravitational forces to have a greater orlesser effect. This makes it possible to adjust the operation and tocompensate for any shortcomings in the distribution which are due to anot entirely suitable felt.

The optimum correspondence between the viscosity of the size and thedensity of the felt is indicated in the table below in the case of a 30°inclination of the felt with respect to the horizontal, a flow length of6 cm, a distribution width of 6 cm and a cylinder pressure on thecoating device of 1 bar:

Viscosity of the size at 20° C. (cP) Density of the felt (g/dm³) <20200-400 20-50 150-250  50-100 125-175 100-250 100-150 250-400 <100

The nature of the felt has an effect on the quality with which the sizeis distributed in respect of three criteria associated with the type offiber employed: the chemical nature of the fibers, their diameter andtheir homogeneity.

The great majority of the fibers making up the felts are composed ofcellulose fibers or wool fibers. Synthetic fibers are also starting tobe used, such as polypropylene fibers or polyester fibers.

In the case of size compositions whose constituents are not very polar,polypropylene-type synthetic felts are very suitable and the chemicalcompatibility is satisfactory. In the case of compositions having amarked polar character (which is the case with many constituentcomponents in sizes), natural felts, of the wool type (which is morehydrophilic), are preferred.

The chemical compatibility of the various materials of the felts may bemodified in one direction or another by a suitable chemical treatment ofthe fibers. However, the interactions with the components of the size(which, because of their monomeric character, are very good solvents)become difficult to control. In most cases, untreated fibers arepreferred.

In general, the diameter of the fibers must be as homogeneous aspossible in order to make it easier to transfer the size onto theroller. Any heterogeneity in the fibers, in particular the presence ofcoarse fibers, causes localized differences in thickness of the film ofsize on the surface of the sizing roller, but these are neverthelessliable to cause drying-induced breakages at the roller. Fibers of smalldiameter (generally 20 microns) are preferred. In addition, the fibersmust be long enough, flexible enough and sufficiently entangled as toavoid any entrainment of entire fibers or breaks at the surface of theroller.

The presence of foreign elements at the surface of the roller generallycauses breakages whose origin is difficult to determine.

In normal operation, more than 95% of the size is transferred onto thesizing roller. To achieve such a performance, it is possible to varydifferent parameters.

In the first place, the pressure exerted by the felt on the roller leadsto the formation of compressed area within the felt through which theflow is very greatly reduced.

However, the pressure must not be too high so as not to damage theroller or the drive mechanisms.

The rotating roller takes up the size available, the latter beingsufficiently compatible with the material of the roller not to cause thephenomenon of dewetting. In addition, the quantity of size is alwaysmuch less than the roller is capable of taking up.

By way of example, in the case of a 40 mm diameter graphite rollerhaving a felt/roller contact length of 80 mm, the pressure that needs tobe exerted is, in most cases, between 0.2 and 2 bar.

Secondly, the speed of rotation of the roller has a certain effect onfelt/roller transfer in a few special cases. Thus, when the size has alow viscosity and the surface of the roller is very effectively wettedthereby (generally, in the case of weakly polar sizes) and/or when thefinal product requires a high loss on ignition, i.e. a large quantity ofsize, it is useful to increase the speed of rotation of the sizingroller in order to increase the take-up area to be wetted and finally toincrease the quantity of size transferred. When a 40 mm diametergraphite roller is used, the rate of rotation of the roller may bevaried between 50 and 150 rpm in order to be satisfactory in most cases.

The third and final parameter to be taken into consideration in thequality of felt/roller transfer is that of the chemical nature and ofthe surface finish of the roller. Moreover, this parameter isincidentally even more significant in respect of the quality ofroller/fiber transfer.

Given that the felt/roller and roller/glass-fiber transfercharacteristics are intimately related, the best material is currentlygraphite or derivatives thereof.

As regards the lateral end regions of the sizing roller 11, whichrarely, or never, come into contact with the filaments 12, and thecorresponding regions of the felt 10, it has been found that, despitethe absence of size take-up by the filaments in these regions, the sizetherein is maintained in the liquid state, not undergoing anycondensation reaction nor any transformation into a more or less solidstate. The observation makes it possible to ascribe this phenomenon tothe presence, within the felt 10, of a flow of size from its lateralregions toward its center, that is to say toward a region in contactwith the filaments, and hence a region in which the size is picked up bythe latter. This flow is due to the movement that the felt 10 is made toundergo according to the invention.

The invention therefore completely solves the gelling problem describedabove.

In normal operation, the technique of depositing anhydrous sizes, asdescribed above, allows a deposition efficiency of very close to orequal to 100% to be achieved. With aqueous sizes, this efficiency isgenerally about 40 to 75%. Given that the cost of the raw materials (interms of dry matter) are substantially equivalent, the economicadvantage of anhydrous sizes deposited using this method is obvious.

In addition, from the environmental standpoint, it is advantageous toeliminate one source of waste which is potentially polluting and givesrise to additional costs in order to destroy the effluents generated.

Should effluent be produced (generally in very small quantity) duringcleaning, testing or operating under special conditions, and given thatall of the waste is of an organic nature, this waste may be easilydestroyed by incineration in suitable plants.

1. A process for manufacturing a continuous yarn from a plurality ofcontinuous filaments formed by the mechanical drawing of a plurality ofstreams of material flowing from orifices of at least one fiberizingdevice, the process comprising: continuously impregnating an absorbentmat with a liquid; continuously transferring at least a portion of theliquid to a rotating roller in contact with the mat; using the roller,depositing the liquid on the surface of at least one of the filamentsbefore the filaments are brought together into at least one yarn;wherein the mat and roller rotate about substantially parallel axes. 2.The process of claim 1, wherein the absorbent mat is formed of fibersthat are mechanically held together.
 3. The process of claim 1, whereinthe absorbent mat is formed of felt or a woven material.
 4. The processof claim 1, wherein the absorbent mat is formed of an elastomeric spongymaterial.
 5. The process of claim 4, wherein the absorbent mat is formedof a foam.
 6. The process of claim 5, wherein the foam is formed frompolyurethane or poly(tetrafluroethylene).
 7. The process of claim 4,wherein the elastomeric spongy material is reinforced.
 8. The process ofclaim 1, wherein the filaments are formed from at least one of polymerand glass.
 9. The process of claim 1, wherein the liquid is an anhydroussize or an anhydrous size component.
 10. The process of claim 1, whereinthe mat and the roller have surfaces that are driven in translationalmovements in substantially the same direction along a line of contact ofthe surfaces.
 11. The process of claim 10, wherein the surface of themat and the surface of the roller are driven in translational movementsin the same sense along the line of contact.
 12. The process of claim11, wherein the speed of the translational movement of the surface ofthe mat is from about 0.5% to about 50% of that of the translationalmovement of the surface of the roller.
 13. The process of claim 10,wherein the surfaces of the mat and roller are driven in translationalmovements in opposite senses along the line of contact.
 14. The processof claim 1, wherein at least two liquids are deposited in succession onthe surface of at least one of the filaments.
 15. The process of claim14, wherein a first liquid is deposited after transfer of the liquidfrom the mat to the roller.
 16. The process of claim 1, wherein theliquid is supplied to the mat by a metering pump.
 17. The process ofclaim 16, wherein the metering pump is a diaphragm pump or a peristalticpump.
 18. The process of claim 16, wherein a fluid circuit is formedbetween the pump and the mat, the fluid circuit comprising a flow meterand a computer for regulating flow of liquid from the pump to the mat.19. The process of claim 1, wherein the liquid is supplied to the mat bydelivering a pressurized gas upstream of a tank of said liquid.
 20. Theprocess of claim 19, wherein a fluid circuit is formed between the tankand the mat, the fluid circuit comprising a flow meter, a regulatingvalve, and a computer for regulating flow of liquid from the tank to themat.
 21. The process of claim 19, wherein a fluid circuit is formedbetween an inlet for supplying the pressurized gas and the tank, thefluid circuit comprising a temperature-compensating volumetricregulating valve.
 22. The process of claim 1, wherein the mat is formedof a material selected from the group consisting of natural felts,synthetic felts, and woven fabrics.
 23. The process of claim 22, whereinthe mat consists essentially of fibers having diameters of less thanabout 20 μm.
 24. The process of claim 1, wherein the mat is formed of amaterial selected from the group consisting of polypropylene, polyester,wool, and cellulose.
 25. The process of claim 1, wherein the roller hassurface micropores with dimensions less than about 10 μm.
 26. Theprocess of claim 25, wherein the surface of the roller is formed of amaterial selected from the group consisting of graphite or graphitederivatives.
 27. The process of claim 1, wherein the liquid transferredto the roller forms a film on the surface of the roller with a thicknessless than about 8 μm.
 28. The process of claim 27, wherein the film hasa thickness between about 3 μm and about 5 μm.
 29. The process of claim1, wherein the liquid is deposited onto the filaments in an amount notexceeding about 3% by weight with respect to the weight of thefilaments.
 30. The process of claim 1, wherein the liquid is depositedonto the filaments in an amount not exceeding about 1% by weight. 31.The process of claim 1, wherein at least two liquids are transferredonto the filaments in succession, with the liquids being capable ofreacting with one another.